Add onundo/redo events, add undo/redo handling to select tool to avoid history desync when undoing with an active selection.

js/lib/commands.js

@@ -21,6 +21,14 @@ const commands = makeReadOnly(
 		_history: [],
 		/** The types of commands we can run (private) */
 		_types: {},
+		
+		/** @type {Observer<{n: int, cancel: function}>} */
+		get onundo() { return this._onundo; },
+		_onundo: new Observer(),
+		
+		/** @type {Observer<{n: int, cancel: function}>} */
+		get onredo() { return this._onredo; },
+		_onredo: new Observer(),
 
 		/**
 		 * Undoes the last commands in the history
@@ -28,6 +36,12 @@ const commands = makeReadOnly(
 		 * @param {number} [n] Number of actions to undo
 		 */
 		async undo(n = 1) {
+			var cancelled = false;
+			await this._onundo.emit({
+				n:n,
+				cancel: ()=>{cancelled=true;},
+			});
+			if (cancelled) return;
 			for (var i = 0; i < n && this.current > -1; i++) {
 				try {
 					await this._history[this._current--].undo();
@@ -45,6 +59,12 @@ const commands = makeReadOnly(
 		 * @param {number} [n] Number of actions to redo
 		 */
 		async redo(n = 1) {
+			let cancelled = false;
+			await this._onredo.emit({
+				n:n,
+				cancel: ()=>{cancelled=true;},
+			});
+			if (cancelled) return;
 			for (var i = 0; i < n && this.current + 1 < this._history.length; i++) {
 				try {
 					await this._history[++this._current].redo();

js/ui/tool/select.js

@@ -23,6 +23,9 @@ const selectTransformTool = () =>
 
 			// Layer system handlers
 			uil.onactive.on(state.uilayeractivecb);
+			
+			commands.onundo.on(state.undocb);
+			commands.onredo.on(state.redocb);
 
 			// Registers keyboard shortcuts
 			keyboard.onShortcut({ctrl: true, key: "KeyA"}, state.ctrlacb);
@@ -65,6 +68,9 @@ const selectTransformTool = () =>
 
 			uil.onactive.clear(state.uilayeractivecb);
 
+			commands.onundo.clear(state.undocb);
+			commands.onredo.clear(state.redocb);
+			
 			// Clear any selections
 			state.reset();
 
@@ -179,6 +185,17 @@ const selectTransformTool = () =>
 						);
 					}
 				};
+				
+				// Undo/Redo Handling, reset state before Undo/Redo
+				state.undocb= (undo)=>{
+					if (state.selected){
+						if (undo.n<=1) undo.cancel();
+						state.reset(false);
+					}
+				}				
+				state.redocb= (redo)=>{
+					if (state.selected){ state.reset(false); }
+				}
 
 				// Mirroring
 				state.togglemirror = () => {